1. Field of the Invention
This invention relates to a hand deviation correction device for correcting hand deviation components of an image, and to a video camera.
2. Description of the Related Art
Recently, a handy type video camera having a charge coupled device (CCD) type image sensor is in widespread use.
Such video camera has a drawback that, since it is hand-held during imaging, hand deviation is liable to be incurred during imaging. If such hand deviation is incurred during imaging, deterioration in the image quality is incurred on reproduction of an image shot with, for example, a zoom-up, thus making the reproduced image extremely ill-looking.
Consequently, such a video camera has recently been marketed on which is loaded a hand deviation correction device for correcting hand deviation caused during imaging.
On the other hand, the techniques such as panning, that is moving the camera in a transverse direction during imaging, or tilting, that is moving the camera from above towards below or vice versa during imaging, are frequently employed in imaging with the video camera.
Referring to FIGS. 1 and 2, a conventional structure of a hand deviation correction device loaded on a video camera is explained. While there are a variety of hand deviation correction systems, one of such systems employing a so-called memory control system is now explained. On detection of hand deviation with the memory control system, part of picture signals imaged by the CCD image sensor of the video camera is taken out as an image frame, an image frame of the previous field and an image frame of the current field are moved into registration with each other depending on the amount of hand deviation for correction of the hand deviation. As a system for detecting the amount of hand deviation, an angular velocity detection system is employed. The angular velocity detection system is such a system in which the angular velocity caused by hand deviation is detected, using an angular velocity sensor formed as a piezo-electric oscillation gyro, and the amount of hand deviation is found based on the detected angular velocity.
Referring to FIG. 1, angular velocity data from an angular velocity sensor is supplied to a terminal 120 and thence to a high-pass filter 121. The high-pass filter 121 is such a filter mainly removing low-frequency components caused by panning or tilting of the video camera from the angular velocity data while directly passing hand-deviation components.
Output data from the high-pass filter 121 is multiplied by a multiplier 127 with a pre-set multiplication coefficient from a total gain adjustment unit 128 so as to be then multiplied with a multiplication coefficient corresponding to a zooming multiplication factor in optical zooming by a multiplier 129 before being sent to a low-pass filter 154. The total gain adjustment unit 128 is provided for producing a multiplication coefficient for correcting fluctuations in the gain of the correction signal from an optical system and an angular velocity sensor of the video camera and which is not necessarily a design mid value. In a zoom gain table 130 are stored plural multiplication coefficients for gain correction associated with zooming multiplication factors for optical zooming of the video camera. The multiplication coefficients corresponding to the current zooming multiplication factors are read out from the zoom gain table 130 so as to be sent to the multiplier 129. Output data of the multiplier 129 is sent to a low-pass filter 154.
The low-pass filter 154 integrates data supplied from the multiplier 129 of the previous stage using an integration coefficient from an integration coefficient table 136.
The integration coefficients stored in the integration coefficient table 136 is related with an integration output of the low-pass filter 154 in a manner as shown for example in FIG. 2. An integration coefficient corresponding to the integrated value by the LPF 154 (LPF integrated value) is taken out from the integration coefficient table 136 and employed in the low-pass filter 154 for integrating data supplied from the multiplier 129. In FIG. 2, the integration coefficients and the LPF integrated values are plotted on the ordinate and abscissa, respectively. Of the LPF integration values of FIG. 2, an integrated value SH corresponds to one-half of the number of pixels in an excess area in the horizontal direction of the CCD image sensor, while an integrated value SV corresponds to one-half the number of pixels in an excess area in the horizontal direction of the CCD image sensor. That is, with the conventional hand deviation correction device, shown in FIG. 2, the correction for hand deviation and convergence during panning or tilting are performed using common integration coefficients.
Output data of the low-pass filter 154 is outputted at a terminal 145 as hand-deviation correction signals. The video camera performs hand deviation correction for correcting deviation components of an image based on the hand deviation correction signals.
However, if common integration coefficients are used for correcting the hand deviation and for convergence for panning or tilting, a correction region for hand deviation cannot be set to a larger value, while follow-up characteristics for panning to tilting are also not optimum. While the linear correction range can be increased for increasing the correction range of amplitude for hand deviation, the amount of residual hand deviation is increased as a secondary effect. Conversely, for improving the follow-up characteristics for panning or tilting, the range for linear correction needs to be diminished, in which case the correction performance is lowered as a secondary effect.
In addition, in the hand deviation correction device employing the conventional memory control system, as shown in FIG. 2, if excess pixels of the CCD image sensor are .+-.40 and .+-.60 in the vertical and horizontal directions, respectively, the number of pixels that can be used in the linear correction region is as small as only .+-.10 pixels, as shown in FIG. 2.